A fuel pump

Abstract: An automotive fuel pump has a pump housing (19) encasing a rotary pumping element (18) which forms two non-communicating chambers (26a, 26b) comprising an inlet chamber (26a) in communication with a fuel inlet (32) and an outlet pumping chamber (26b) in communication with a fuel outlet. The rotary pumping element (18) has a ring portion (60) along an outer circumference, a plurality of vanes (56) around an inner circumference radially inward of the ring portion (60), and a plurality of axially extending fuel flow passages (62) located radially between the plurality of vanes and the ring portion. Fuel passes from the fuel inlet (32) to the outlet pumping chamber (26b) and from the inlet pumping chamber (26a) to the fuel outlet (22) through the fuel flow passages (62) in the rotary pumping element (18).

Description: This invention relates to automotive fuel pumps, and, in particular, to a fuel pump housing and rotary pumping element which combine to form two pumping chambers for reducing the tolerances required in manufacturing and for minimising crossing losses. Conventional tank-mounted automotive fuel pumps typically have a rotary pumping element, 118 encased within a pump housing, 120, as shown in Figures 2 and 3. Fuel flows into pumping chamber 124 within pump housing 120 and the rotary pumping action of vanes 126 and vane grooves 128 of rotary pumping element 118 produces vortices 132. Vanes 126 do no, however, extend to the top, 130, of pumping chamber 124 and fuel crosses between sides 134 and 136. An additional problem with conventional fuel pump designs is the need for stripper portion 122 in pump housing 120 (Figure 2). As fuel is propelled by rotary pumping element 118 from the fuel inlet (not shown) to the fuel outlet (not shown), fuel pressure increases. Since the fuel inlet and fuel outlet are nearly circumferentially adjacent, stripper portion 122 must be closely toleranced with respect to rotary pumping element 118 so as to separate low pressure region 110 from high pressure region 112 near the inlet and outlet, respectively, without undue losses. Stripper portion 122 increases the manufacturing cost because close tolerancing is required A conventional fuel pump is shown in DE-A-3 118 533 for example. The present invention provides a more efficient fuel pump which minimises crossing losses within the pumping chamber by providing two pumping chambers on opposed sides of the pumping element and by providing the pumping element with an outer ring portion which eliminates the need for a stripper. According to the invention we provide a fuel pump for supplying fuel from a fuel tank to an automotive engine, comprising: a pump casing; a motor mounted within said casing and having a shaft extending therefrom; a rotary pumping element fitted to said shaft having a ring portion along an outer circumference thereof, a plurality of vanes around an inner circumference radially inward of said ring portion, and a plurality of axially extending fuel flow passages located radially between said plurality of vanes and said ring portion; and a pump housing mounted within said pump casing and having a fuel inlet and a fuel outlet therethrough, said pump housing encasing said rotary pumping element therein: characterised in that two axially spaced pumping chambers connected in series by said flow passages are formed along the periphery of, and on opposite sides of, the pumping element. The two pumping chambers comprise an inlet pumping chamber in communication with the fuel inlet and an outlet pumping chamber in communication with the fuel outlet, with the fuel passing from the fuel inlet to the outlet pumping chamber and from the inlet pumping chamber to the fuel outlet through the fuel flow passages in the rotary pumping element. A fuel pump embodying the present invention provides a fuel pump housing and rotary pumping element design which eliminates the need for machining the pump bottom of a pump housing or for providing a barrier between the high and low pressure regions of the pumping chamber. The two pumping chambers of the fuel pump minimise crossing losses within the pump housing. The fuel pump embodying the invention has a rotary pumping element having an outer ring portion which fits snugly within the pump bottom of the pump housing so that the pump bottom does not require a stripper portion and thus simplifies the manufacture thereof. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a fuel pump according to the present invention. Figure 2 is a sectional view, partly broken away, of a prior art rotary pumping element within a fuel pump housing showing a stripper portion for separating high pressure and low pressure areas of the pumping chamber. Figure 3 is a cross-sectional view of a prior art pumping chamber showing the shape of the flow channels in the top and bottom portions of the pump housing. Figure 4 is a sectional view, partly broken away, of a rotary pump according to the present invention. Figure 5 is a cross-sectional view of a portion of a pump according to the present invention showing non-communicating pumping chambers in the top and bottom portions of the pump housing. Figure 6 is view taken along line 6-6 of Figure 4 showing vane and vane groove detail of a rotary pumping element according to the present invention. Figure 7 is view taken along line 7-7 of Figure 4 showing vane, fuel flow passage and vane groove detail of a rotary pumping element according to the present invention. Figure 8 is a cross-sectional view of a portion of a pump according to the present invention showing fuel flow from the fuel inlet to the outlet pumping chamber of the pump housing. Figure 9 is a cross-sectional view of an outlet portion of a pump according to the present invention showing fuel flow from a narrower and shallower offset section of the inlet pumping chamber to the fuel outlet of the pump housing. Figure 10 is perspective view of a pump housing and rotary pumping element according to the present invention showing a pump cover and a pump bottom which comprise the pump housing. Figure 11 is a perspective view of the rotary pumping element mating face of a pump cover according to the present invention showing an annular pumping channel which converges and bends radially outward toward one circumferential end. Referring now to Figure 1, fuel pump 10 has casing 12 for containing motor 14, preferably an electric motor, which is mounted within motor space 36. Motor 14 has shaft 16 extending therefrom in a direction from fuel pump outlet 44 to fuel inlet 32. Rotary pumping element 18, preferably an impeller, or, alternatively, a regenerative turbine, is fitted on shaft 16 and encased within pumping section 19, which preferably is composed of pump bottom 20 and pump cover 30, as shown in Figure 10. Rotary pumping element 18 has a central axis which is coincident with the axis of shaft 16 (Figure 1). Shaft 16 passes through shaft opening 40 of rotary pumping element 18 and into cover recess 38 of pump cover 30. As seen in Figure 1, shaft 16 is journalled within bearing 24. Pump bottom 20 has fuel outlet 22 leading from a pumping chamber 26 formed along the periphery of rotary pumping element 18. Pressurised fuel is discharged through fuel outlet 22 to motor space 36 and cools motor 14 while passing over it to fuel pump outlet 44. Figures 4 and 10 show the preferred embodiment of rotary pumping element 18 of the present invention. Rotary pumping element 18 has an outer ring portion 60 radially along an outer circumference thereof which mates with annular inner ledge 21 of pump bottom 20 (Figure 10). Housing mating face 17 of rotary pumping element 18 thus will be flush, in a perpendicular direction to the axis of shaft 16, with annular outer ledge 23 within shoulder 25 of pump bottom 20. A plurality of vanes 56 extend around an inner circumference of rotary pumping element 18 radially inward of outer ring portion 60 (Figure 4). Circumferentially adjacent to vanes 56 are vane grooves 58 preferably having a semi-circular shape which, as discussed below, approximates the shape of fuel flow vortices within pumping section 19. Radially between outer ring portion 60 and vanes 56 are a plurality of fuel flow passages 62, preferably arcuate slots, which extend through rotary pumping element 18 parallel to the axis of shaft 16 (Figure 7). Flow passages 62 preferably have a radial width of one-half or greater than the radial length of a vane 56. The circumferential length of flow passages 62 is preferably equal to or less than the circumferential distance, in a perspective along an axis parallel to shaft 16, between fuel inlet 32 and fuel outlet 22. Rotary pumping element 18 is preferably integrally moulded out of a plastic material, such as phenolic, acetyl or other plastic or non-plastic materials known to those skilled in the art. Alternatively, rotary pumping element 18 can be die cast in aluminium or steel. In order to minimise the crossing losses previously discussed, two pumping chambers 26a and 26b are formed on opposite sides of rotary pumping element 18 as shown in Figure 5. Annular cover channel 68 and annular bottom channel 70, which cooperate with vane grooves 58 to form pumping chambers 26a and 26b, respectively, are fashioned circumferentially along a radially outward portion of rotary pumping element mating surfaces 46 and 48 of pump cover 30 and pump bottom 20, respectively, as shown in Figures 10 and 11. Rotary pumping element 18 mates with mating face 46 on the side adjacent pump cover 30 and with inner ledge 21 of pump bottom 20 to prevent fuel from flowing between pumping chambers 26a and 26b (Figure 5). Preferably, rotary pumping element 18 has an inner ring portion 64 radially disposed between vanes 56 and fuel flow passages 62 to prevent fuel from flowing between inlet pumping chamber 26a and outlet pumping chamber 26b. Additionally, it is preferable for inlet pumping chamber 26a and outlet pumping chamber 26b to have circular shaped cross-sections, as shown in Figure 5, which approximate the shape of primary vortices 66 and which prevent secondary counter flowing vortices from forming. With the rotary pumping element 18 and pumping section 19 just described, pump bottom 30 is more easily manufactured since there is no need for the stripper portion previously discussed. Thus, the exactness in tolerancing necessary of prior art rotary pumping elements is no longer required since rotary pumping element 18 of the present invention has outer ring portion 62 which fits snugly within shoulder 25 of pump bottom 20. In operation, fuel is drawn from a fuel tank (not shown), in which pump 10 may be mounted, through fuel inlet 32 in pump cover 30, and into pumping chambers 26a and 26b by the rotary pumping action of rotary pumping element 18 (Figure 8). As rotary pumping element 18 rotates, fuel flow passages 62 intermittently provide a path for fuel to flow from a flared section 33 of inlet pumping chamber 26a to a flared section 76 of outlet pumping chamber 26b axially aligned with fuel inlet 32 (Figure 10). The rotary pumping action of vanes 56 on rotary pumping element 18 propels primary vortices 66 circumferentially around annular pumping chambers 26a and 26b (Figure 5). Fuel flow from pump housing 19 to motor space 36 is accomplished as shown in Figure 9. Fuel flow passages 62 intermittently provide a path for fuel to flow from a narrower and shallower transition section 72 of inlet pumping chamber 26a to a flared section 78 of outlet pumping chamber 26b axially aligned with transition section 72 and adjacent fuel outlet 22. Fuel from outlet pumping chamber 26b is exhausted through fuel outlet 22. Transition section 72 of pump cover 30 preferably extends along an angle of approximately 15°-25° in which the depth of cover channel 68, as measured from the centre of cover channel 68 to rotary pumping element mating face 46 of pump cover 30, gradually decreases until cover channel 68 is flush with mating face 46 at cover channel end 73. Cover face 46 mates with rotary pumping element 18 when pump cover 30 and pump bottom 20 are combined. Cover channel 68 depth is approximately 0.5 to 2.0 mm from fuel inlet 32 to a transition beginning point 74 of transition section 72. The width of cover channel 68 gradually narrows to a point at cover channel end 73. This gradual convergence of cover channel 68 provides a smooth path for vortices 66 to migrate toward fuel outlet 22 without the cross-over losses inherent in fuel flow channels axially adjacent the fuel outlet. Cover channel 68 extends approximately 285°-295° from fuel inlet 32 to transition beginning point 74 (Figure 11). As seen in Figure 1, a purge orifice 34 extends axially through pump cover 30 to bleed fuel vapour from pumping chamber 26a so that vapourless liquid fuel reaches the engine (not shown). Fuel vapour passes from pumping chamber 26a, through purge orifice 34, and into the fuel tank (not shown). Preferably, purge orifice 34 is located at a radially inward portion of cover channel 68 approximately 100°-120° from fuel inlet 32 as shown in Figure 11. Cover channel 68 and bottom channel 70 can be die cast along with pump bottom 20 and pump cover 30, preferably in aluminium, or can be machined into pump bottom 20 and pump cover 30. Alternatively, cover channel 68 and bottom channel 70 can be integrally moulded together with pump bottom 20 and pump cover 30 out of a plastic material, such as acetyl or other plastic or non-plastic materials known to those skilled in the art.

Claims: A fuel pump for supplying fuel from a fuel tank to an automotive engine, comprising: a pump casing (12); a motor (14) mounted within said casing (12) and having a shaft (16) extending therefrom; a rotary pumping element (18) fitted to said shaft (16) having a ring portion (60) along an outer circumference thereof, a plurality of vanes (56) around an inner circumference radially inward of said ring portion (60), and a plurality of axially extending fuel flow passages (62) located radially between said plurality of vanes (56) and said ring portion (60); and a pump housing (19) mounted within said pump casing (12) and having a fuel inlet (32) and a fuel outlet (22) therethrough, said pump housing (19) encasing said rotary pumping element therein: characterised in that two axially spaced pumping chambers (26a, 26b) connected in series by said flow passages (62) are formed along the periphery of, and on opposite sides of, the pumping element (18). A fuel pump according to claim 1 wherein said pumping chambers (26a, 26b) comprise an inlet pumping chamber (26a) in communication with said fuel inlet (32) and an outlet pumping chamber (26b) in communication with said fuel outlet (22), with fuel passing from said fuel inlet (32) to said outlet pumping chamber (26b) and from said inlet pumping chamber (26a) to said fuel outlet (22) through said fuel flow passages (62) in said rotary pumping element (18). A fuel pump according to either claim 1 or claim 2 wherein said rotary pumping element (18) has an inner ring portion (64) located radially between said vanes (56) and said flow passages (62) for separating said pumping chambers (26a, 26b). A fuel pump according to any one of the preceding claims wherein said plurality of flow passages (62) comprise arcuate slots with a radial width of one-half or greater than the radial length of one of said plurality of vanes (56). A fuel pump according to any one of the preceding claims wherein said plurality of vanes (56) are separated by a plurality of semi-circular vane grooves (58). A fuel pump according to any one of the preceding claims wherein said rotary pumping element (18) comprises a regenerative impeller.

Inventors: BROCKNER HENRY W, YU DEQUAN, BROCKNER, HENRY W., YU, DEQUAN
Applicants: FORD MOTOR CO, FORD MOTOR COMPANY
Application year: 1994
Main classification: F04D5
IPC codes: F02M37, F04D5, F04D29, F04B53